Life history examination of darkblotched rockfish (Sebastes crameri) off the Oregon coast Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/hh63sz46z

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  • The growth, size and age composition, mortality and reproduction of darkblotched rockfish (Sebastes crameri) were examined using fishery data and analysis of fish characteristics for samples collected of f the Oregon coast. A total of 1060 fish, caught by commercial groundfish and shrimp trawlers operating out of Newport, Coos Bay and Astoria, were collected between July 1986 and July 1987. S. crameri were found to be slow growing and longlived reaching ages in excess of 100 years. The composition of fish captured with commercial groundfish trawl gear (excluding shrimp gear) was dominated by recent recruits ranging from 6 to 9 years of age. The age at full recruitment to commercial groundfish gear was 7 years. Assuming constant recruitment and mortality after 1978, total instantaneous mortality (Z) for recent recruits may have been as high as 0.42. This estimate may be inflated, however, if the 1978-1980 yearclasses were strong relative to earlier yearclasses. The timing of major reproductive events was protracted. Insemination occurred from September to December, fertilization from December to February, and parturition from December to March. Fifty percent of the females were mature at an age of 8 years and a total length (TL) of 36.7 cm, whereas males attained 50% maturity at an age of 5 years and 29.7 cm TL. Fecundity increased nonlinearly with fish size and ranged from 19,815 to 489,064 oocytes/ovary pair. Based on its longevity, its relatively young age at full recruitment, and its age at maturity, S. crameri appears vulnerable to overexploitation.
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